Method of producing a unitary turbine wheel having twisted blades by electrolytic fabrication

ABSTRACT

A method of producing a unitary turbine wheel having twisted blades by electrolytic fabrication, wherein the cross sectional shape of the blades is defined by predetermined radii of curvatures or predetermined radii of curvatures and a straight line connected therewith, and electrodes respectively complementary in shape to the concaved and convexed faces of the blades are fed into the space between the adjacent blade portions of a wheel blank each at a time to electrolytically fabricate said concaved and convexed faces of each blade individually separately.

United States Patent 1191 Kawafune et al.

1451 Apr. 9, 1974 METHOD OF PRODUCING A UNITARY TURBINE WHEEL HAVING TWISTED BLADES BY ELECTROLYTIC FABRICATION Inventors: Kazuyoshi Kawafune, Komae;

Kouichi Noto, Yokohama, both of Japan Assignee: Hitachi, Ltd., Tokyo, Japan Filed: Dec. 28, 1971 Appl. No.: 213,103

[30] Foreign Application Priority Data Dec. 28, 1970 Japan 45-120440 US. or. 204/129.1, 204/224 M 1m. 01 823p 1/00 Field of Search 204/224 M, 129.1, 129.5,

References Cited UNITED STATES PATENTS 8/1970 Stark et al. 204/DIG. I2

3,058,895 10/1962 Williams ..204/DIG.l2

FOREIGN PATENTS OR APPLICATIONS 198,871 1 6/1967 U.S.S.R 204/DIG. l2

Plifllfll') E.\'aminerF. C. Edmundson Attorney, Agent, or F irm-Craig and Antonelli 29 Claims, 7 Drawing Figures PATENTEUAPR 9 I974 SHEET 2 [IF 2 METHOD OF PRODUCING A UNITARY TURBINE WHEEL HAVING TWISTED BLADES BY ELECTROLYTIC FABRICATION.

BACKGROUND OF THE INVENTION 1. Summary of the Invention This invention relates. to a method of producing a unitary turbine wheel having twisted blades, for use in a gas turbine or steam turbine, from a blank material. by electrolytic fabrication.

2. Description of the Prior Art Inthe production of this type of impellers, it has been customary to fabricate the individual blades mechanically. or electrolytically separately from the disc and plant the thus fabricated blades in the disc by the christmas tree devetail. method. This is' because of the reason. which will be described hereunder: Referring to FIGS. 1 and2. there isexemplifieda turbine wheel having twisted blades, in which reference numeral-.1 designates the outer edge of the blade V, 2 the root of the blade and 3 the disc. Each. blade V is twistedfrom the outer edge to the rootthereof. FIG. 3 is asectional view taken on. the linev IIIF-lllf of FIG. 2 and showing. the

shape of the blades in the longitudinal direction thereof. In the production of. such a type of turbinewheel, if the-blades are formedintegrally with the disc and electrolytically. shaped. by inserting an electrode i'nto the space 4 between the adjacent blades V and V in the. direction ofthearrow E the unnecessary blank material 5 would remain at the root of the blade V and if the electrode is insertedinthedirectionof the arrow E so as to eliminatesuch:unnecessary blank ma? terial, the unnecessary blank material 6 would remain at the inner flankzof; the blade V Thus, by the electrolytic fabrication'using an electrode, it is impossible to accomplish shaping of the bladesin one step.

Furthermore, since the. blades are. twisted as shown in FIG. 2', a methodof leaving the blade shape within the electrode cannot be employed, which has been employed in the fabrication of straight bladeshaving a uniform cross section.

For the above reasons, ithas been regard as impossible to fabricate a unitary turbine blade'having twisted SUMMARY OF THE INVENTION The object-of the present invention is to provide a method by which the production of a unitary turbine wheel having twisted blades-by electrolytic fabrication is possiblewhich has been regardedas impossible here.- tofore.

BRIEF DESCRIPTIONOF THE DRAWING- FIG. 1 is a perspectiveview of aturbine wheel having.

twisted blades; 7

FIG. 2 is a plan view ofaportion of'FIG. 1;

FIG. 3is a sectional view taken on the.line IIIIII of FIG. 2;

FIGS; 4 and S'areviews for'eitplainingthe shape of the blades according to thepresent invention respectively;

FIG. 6 is a plan view showing the mode of carrying out the electrolytic fabrication according to the method of this invention; and

FIG. 7 is a sectional view taken on the line VIIVII of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. 4 through 7.

First of all, the shape of the blades of the turbine wheel produced by the method of this invention will be described with reference to FIGS. 4 and 5. Reference character R designates the radius of curvature of the concaved face of the blade V, R the the radius of curvature of the convexed face of the blade V, A, and B, the centers of 'the radii of curvatures of the concaved and convexed faces of the blade at the outer edge respectively, and A and B the centers of the radii of curvatures of the concaved and convexed faces of the blade at the root respectively.

The concaved face has a straight portion in contact with the radius of curvature R As shown in FIG. 5, the centers of the radii of curvatures R and R respectively lie on straight lines inclined at angles of 0,, and O to the center line L of the blade V. The intersection a of the radius of curvature R, of the concaved face with the straight portion lies on a line 7 in FIG. 5 which is parallel to the line connecting A and A FIGS. 6 and7 show the mode of shaping by electrolytic fabrication the blade of the shape explained with reference to FIGS. 4 and 5. 7

Namely, FIG. 6 is a plan view showing the state in which the convexed face of the blade is being shaped after the concaved face has been shaped. Reference numeral 8 designates a slit used for the shaping of the concaved face, 9 and 10 electrodes used for shaping the concaved face and the convexed face, 11 an electrolyte discharge slit and 12 the radius of curvature of the electrode 10 which is set at a value which is the sum of the radius of curvature R and a space required for the electrolytic fabrication.

FIG. 7 is a sectional view taken on the line VIIVII of FIG. 6, in which the arrow E indicates the feeding direction of the electrode 10. This direction is a direction from the outer edge of the blade toward the center B and a direction from the root of the blade toward the center B Reference numeral 13 designates an insulating guide for applying a back pressure to equalize the flow of electrolyte, which is not apparent in FIG. 6.

The flow direction of the electrolyte is indicated by the arrow 14. 'i I I As stated above, the shape of the electrode is determined in consideration of the radius of curvature R of the blade, and the electrode is fed while maintaining the center of the radius of curvature thereof at the centers B B of the radii of curvatures of the blade, whereby the convexed face of the blade can be shaped.

The shaping of the concaved face, i.e., the portion indicated at'9, can be accomplished in the same manner. The concaved face has a straight portion in contact with the radius of-curvature R; but the electrode used for shaping the concaved face can be produced in the same manner as that used for shaping the convexed face. In the fabrication of the concaved face, the electrode is fed while maintaining the center of the radius of curvature thereof at the centers A A Upon completion of the fabrication of one blade, indexing is performed by using an indexing plate and the fabrication of the next blade is carried out, after which the above-described operation is repeated.

In FIG. 7, plate-shaped portions formed on both sides of the blade are removed when the root 16 of the blade is cut by a lathe upon completion of fabrication of the entire blades. The edges 17, 180i the blade shown in FIG. 6 cannot be shaped with an accurate radius of curvature, only by the fabrication method of this invention and some amount of the blank material remains. The accurate radius of curvature is imparted by an electrochemical method.

Now, a practical example of practicing the method of this invention will be illustrated hereunder:

A blade having a length of 150 mm, a radius of curvature of the concaved face of 41.7 mm and a radius of curvature of the convexed face of 31.4 mm was fabricated under the conditions that the applied voltage was 15 V, the feeding speed of the electrodes was 1.5 mm/min and the pressure of the electrolyte was l3 Kg/cm, and a good result was obtained.

As described herein, according to the present invention a unitary turbine wheel having twisted blades can be produced efficiently by electrolytic fabrication. The present invention is particularly advantageously used in the production of large-sized turbine wheels.

We claim:

1. A method of producing a twisted blade turbine wheel having at least one twisted blade and a disc integral therewith by electrolytic fabrication from a block of material, each of said at least one twisted blades having a root end merging with said disc and an outer tip end, the cross-sectional shape of each of saidtip and root ends exhibiting respective concave and convex sides with respective constant radii of curvature over the length of the blade between the tip and root ends; said method comprising:

supplying en electrolyte to a concave electrode and applying a voltage to said electrolyte while moving said concave electrode into said block of material with the center of the radius of curvature of the concave electrode moving in a first straight line interconnecting the center of the radius of curvature of the tip end of the concave side of the blade with the center of the radius of curvature of the root end of the concave side of the blade, to thereby electrolyitically form the concave side of the blade, and supplying an electrolyte to a convex electrode and applying a voltage to said electrolyte while moving said convex electrode into said block of material with the center of the radius of curvature of the convex electrode moving in a second straight line interconnecting the center of the radius of curvature of the tip end of the convex side of the blade with the center of the radius of curvature of the root end of the convex side of the blade, to thereby 'electrolyitically form the convex side of the blade,

wherein said first and second straight lines are inclined at a predetermined angle with respect to one and separately from one another during the aboveidentified moving steps,

3. A method according to claim 1, wherein, at the root end of the blade being formed, the centers of the radii of curvature of both said concave and convex sides of the blade are located on a circumferential line around said disc. which interconnects respective radially extending blade centerlines of adjacent blades.

4. A method according to claim 1, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.

5. A method according to claim 1, wherein said first and second straight lines are inclined at respective different predetermined angles with respect to a blade centerline which extends radially from the tip end to the root end of the blade being formed.

6. A method according to claim 5, wherein said first straight line is inclined with respect to said blade centerline by an amount greater than said second straight line.

7. A method according to claim 5, wherein said concave and convex electrodes are moved independently and separately from one another during the aboveidentified moving steps.

8. A method according to claim 7, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.

9. A method according to claim 7, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps,

and wherein said steps of moving said respective electrodes into said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.

10. A method according to claim 9, wherein said pre' determined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.

11. A method according to claim 10, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade ina similar manner at said new forming station.

12. A method according to claim 7, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed. A

13. A method according to claim 1, wherein the cross-sectional shape of said blade is delimited by the respective radii of curvature of said concave and convex sides and by straight lines tangential therewith, and wherein respective intersections of said radii of curvature and straight lines tangential therewith are located on respective straight lines extending parallel to respective ones of said firstand second straight lines.

14. A method according to claim 13, wherein, at the root endof the blade being formed, the centers of the radii of curvature of both said concave and convex sides of the blade are located on a circumferential-line around said disc which interconnects respective radially extending blade centerlines of adjacent blades.

15. A method according to claim 13, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps,

and wherein said steps of moving said respective electrodes into said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.

16. A method according to claim 15, wherein said predetermined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.

17. A method according to claim 16, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.

18. A method according to claim 17, further comprising cutting off said flat land portions after said concave and convex sides have been formed.

19. A method according to claim 18, further comprising cutting off said flat land portions after said concave and convex sides have been formed.

20. A method according to claim 19, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.

21. A method according to claim 1, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps,

and wherein said steps of moving said respective electrodes into said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.

22. A method according to claim 21, wherein said predetermined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.

23. A method according to claim 21, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.

24. A method according to claim 23, further comprising cutting off said flat land portions after said concave and convex sides have been formed.

25. A method according to claim 23, further comprising cutting off said flat land portions after said concave and convex sides have been formed.

26. A method according to claim 1, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.

27. A method according to claim 26, further comprising cutting off said flat land portions after said concave and convex sides have been formed.

28. A method according to claim 26, further comprising disposing an insulating guide on the respective flat land at one side of said blade being formed for guiding and uniformalizing the flow of electrolyte during movementof said respective electrodes to form said convex and concave sides of a blade.

29. A method according to claim 28, further comprising cutting off said flat land portions after said concave and convex sides have been formed. 

2. A method according to claim 1, wherein said concave and convex electrodes are moved independently and separately from one another during the above-identified moving steps,
 3. A method according to claim 1, wherein, at the root end of the blade being formed, the centers of the radii of curvature of both said concave and convex sides of the blade are located on a circumferential line around said disc which interconnects respective radially extending blade centerlines of adjacent blades.
 4. A method according to claim 1, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.
 5. A method according to claim 1, wherein said first and second straight lines are inclined at respective different predetermined angles with respect to a blade centerline which extends radially from the tip end to the root end of the blade being formed.
 6. A method according to claim 5, wherein said first straight line is inclined with respect to said blade centerline by an amount greater than said second straight line.
 7. A method according to claim 5, wherein said concave and convex Electrodes are moved independently and separately from one another during the above-identified moving steps.
 8. A method according to claim 7, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.
 9. A method according to claim 7, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps, and wherein said steps of moving said respective electrodes into said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.
 10. A method according to claim 9, wherein said predetermined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.
 11. A method according to claim 10, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.
 12. A method according to claim 7, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.
 13. A method according to claim 1, wherein the cross-sectional shape of said blade is delimited by the respective radii of curvature of said concave and convex sides and by straight lines tangential therewith, and wherein respective intersections of said radii of curvature and straight lines tangential therewith are located on respective straight lines extending parallel to respective ones of said first and second straight lines.
 14. A method according to claim 13, wherein, at the root end of the blade being formed, the centers of the radii of curvature of both said concave and convex sides of the blade are located on a circumferential line around said disc which interconnects respective radially extending blade centerlines of adjacent blades.
 15. A method according to claim 13, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps, and wherein said steps of moving said respective electrodes into said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.
 16. A method according to claim 15, wherein said predetermined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.
 17. A method according to claim 16, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.
 18. A method according to claim 17, further comprising cutting off said flat land portions after said concave and convex sides have been formed.
 19. A method according to claim 18, further comprising cutting off said flat land portions after said concave and convex sides have been formed.
 20. A method according to claim 19, further comprising indexing the block of material to a new blade forming position upon the formation of a respective blade, and sequentially forming another similar blade in a similar manner at said new forming station.
 21. A method according to claim 1, wherein said steps of supplying of said electrolyte includes forcing said electrolyte at a predetermined pressure from electrolyte openings formed at the centers of the respective electrodes into electrolyte supply gaps, and wherein said steps of moving said respective electrodes intO said block of material include moving said respective electrodes at a constant rate from the tip end to the root end of the respective blade being formed.
 22. A method according to claim 21, wherein said predetermined pressure is a constant pressure for movement from the tip end to the root end of a respective blade being formed.
 23. A method according to claim 21, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.
 24. A method according to claim 23, further comprising cutting off said flat land portions after said concave and convex sides have been formed.
 25. A method according to claim 23, further comprising cutting off said flat land portions after said concave and convex sides have been formed.
 26. A method according to claim 1, wherein said steps of moving said respective electrodes includes forming flat land portions in said block of material at the respective concave and convex sides of said blade being formed.
 27. A method according to claim 26, further comprising cutting off said flat land portions after said concave and convex sides have been formed.
 28. A method according to claim 26, further comprising disposing an insulating guide on the respective flat land at one side of said blade being formed for guiding and uniformalizing the flow of electrolyte during movement of said respective electrodes to form said convex and concave sides of a blade.
 29. A method according to claim 28, further comprising cutting off said flat land portions after said concave and convex sides have been formed. 